Year
Event
1314
Birth of Prince U-Thong, the future first king of Ayutthaya.

[Reference: The Rise of Ayutthaya - Charnvit Kasetsiri (1976) - page 157]
1324
Construction of the statue of Phra Phanan Choeng (presently at Wat Phanan Choeng - Ayutthaya).
1325
Phya U-Thong, father-in-law of Ramathibodi I, acquired a considerable part of the dominions once ruled over by King Ramkhamhaeng of Sukhothai.
These dominions, include Nakhon Sri Thammarat, Ratburi and Phetburi, as well as Tenasserim and Tavoy, which had been lost to Sukhothai in 1318, and
which U-Thong had annexed around 1325.

[Reference: A History of Siam - W.A.R. Wood - Chap IV - page 63]
1331
Prince U-Thong married a princess of Suphanburi.

[Reference: The Rise of Ayutthaya - Charnvit Kasetsiri (1976) - page 157]
1340s
Prince U-Thong married a princess of Lopburi.

[Reference: The Rise of Ayutthaya - Charnvit Kasetsiri (1976) - page 157]
1347
Death of King Loethai of Sukhothai and throne ascendancy of King Mahathammaracha I (Luthai). The Sukhothai dominions are invaded by Prince
U-Thong and Chainat captured, but returned on unknown conditions.

[Reference: A History of Siam - W.A.R. Wood (1924) - page 65]
1350
Founding of Ayutthaya and commencement of the Kingdom of Siam.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 10]
1351
Throne ascendancy of King Ramathibodi I (U-Thong) on 4 March 1351 - 1st King of Ayutthaya. King Ramathibodi installed his brother-in-law, Prince
Phangoa, as governor of Suphanburi, with the title of Borommaracha Thao. His son, Prince Ramesuan, was appointed governor of Lopburi.
1352
Ayutthaya attacked Angkor. King Ramathibodhi I send his son, Prince Ramesuan with an army to Angkor after a new King - Boromma Lamphongsaraja -
succeeded the Cambodian throne. Prince Ramesuan's vanguard got routed, fled and collided with his main army. Prince Phangoa (the later King
Borommaracha I) of Suphanburi was asked to assist. He defeated the Cambodians and the Khmer capital was taken in 1353 after a siege of one year. As
the King of Cambodia died during the siege, a vassal king was set up in his place. A large number of Khmer inhabitants were moved to Ayutthaya.

[Reference: The Royal Chronicles of Ayutthaya - Cushman - page 11 / A History of Siam - W.A.R. Wood - Chap IV - page 65]

Thai scholars although put this campaign against Cambodia in the year 1369.

[Reference: The Rise of Ayutthaya - Charnvit Kasetsiri (1976) - page 123]
1353
Construction of Wat Phutthai Sawan at the Wiang Lek Royal Residence. It is from this place that U-Thong sent out his men to find a suitable location to
establish the city of Ayutthaya. It was one of the customs of the Northern Kingdom of Sukhothai to turn the Royal residence into a temple. King
Borommatrailokanat would later follow this example in giving the location of his palace to establish
Wat Sri Sanphet.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 11 / The Rise of Ayutthaya - Charnvit Kasetsiri (1976) - page 136]
1363
Construction of Wat Pa Kaeo, presently called Wat Yai Chai Mongkhon. King Ramathibodhi I ordered the construction of a chedi and vihara at the
cremation site of Prince Keo and Prince Thai (probably sons from one of his three wives) who died from cholera and gave it the name of Pa Kaeo.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 11].

William Wood put the death of the two princes in 1357 (his source is not known).  

[Reference: A History of Siam - W.A.R. Wood (1924) - page 65]
1369
See 1352
1369
Construction of Wat Phra Ram.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 11]
1369
Death of King Ramathibodhi I and throne ascendancy of King Ramesuan - 2nd King of Ayutthaya.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 11]
1370
Throne ascendancy of King Borommaracha I - 3th King of Ayutthaya. King Ramesuan was unpopular. A year after his accession to the throne,
disturbances broke out which he was unable to quell. He was urged by his ministers to abdicate in favour of his uncle, Prince Phangoa at that time the
governor of Suphanburi. The matter was amicably arranged. Prince Phangoa became King under the name of Borommaracha I, while King Ramesuan
reverted to his former position as Governor of Lopburi.

[Reference: A History of Siam - W.A.R. Wood (1924) - page 70]
1371
King Borommaracha I sends an embassy to Nankin - China (Hongwou, 1st Emperor of the Ming Dynasty) to inform him of the changes at the Court in
Ayutthaya.

[Reference: A History of Siam - W.A.R. Wood (1924) - page 71]
1371
King Borommaracha I invades Sukhothai and captures several northern towns.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 11]
1372
King Borommaracha I continues his annexations and seizes Nakhon Phangkha and Saeng Charao.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 12]
1373
King Borommaracha I invests the city of Chakangrao (Kamphaengphet) the western outpost of the Sukhothai dominions. Phraya Sai Kaeo, one of the
rulers was killed in battle, while another ruler, Phraya Khamhaeng, was able to flee back into the fortified city. The Ayutthayan army returned without
capturing the city.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 12]
1373
A Siamese princess, probably the mother of the ex-King Ramesuen sent envoys to Nankin (China).

[Reference: A History of Siam - W.A.R. Wood (1924) - page 71]
1373
Ayutthaya established the town of Tenasserim in 1373 and built the pagoda of Wottsheng finalized in 1380, still standing on the ruins of Old Tenasserim.

[Ref: English Intercourse with Siam in the 17th century - John Anderson (1890) - Page 3.]
1374
King Borommaracha I's nephew, Prince Nakhon In  (later King Intharacha - Inburi, city under Suphanburi), sent envoys to Nankin (China).

[Reference: A History of Siam - W.A.R. Wood (1924) - page 71]
1374
(Approx) Throne ascendancy of Maha Thammaracha II of Sukhothai.

[Reference: The Rise of Ayudhya - Chranvit Kasetsiri (1976) - App A]
1375
A son of the ex-King Ramesuan sent an embassy to Nankin (China).

[Reference: A History of Siam - W.A.R. Wood (1924) - page 71]
1375
Prince Nakhon In visits Nankin in person.

[Reference: A History of Siam - W.A.R. Wood (1924) - page 71]
1375
King Borommaracha I seized Phitsanulok, the second capital of the Kingdom of Sukhothai. The ruler of the city, Khun Sam Kaeo, is captured and a large
number of Phitsanulok's inhabitants is forcibly moved to Ayutthaya.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 12]
1376
King Borommaracha I makes another attempt to take Chakangrao. The Governor of Chakangrao received assistance from the Governor of Nan and his
army.   They set up an ambush for the Ayutthayan army, but did not succeed. The troops of the Governor of Nan were scattered and slaughtered. The
city of Chakangrao although was able to resist and King Borommaracha I returned to Ayutthaya.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 12 / A History of Siam - W.A.R. Wood (1924) - page 72]
1377
Establishment of Mueang Indra (Inburi) by Khun Luang Pha Ngua (King Borommaracha I) in 1377.

[Ref: Ancient Cities in Thailand - Abha Bhamorabutr (1981) - page 19.]
1378
King Borommaracha I went to seize Sukhothai's frontier city, Chakangrao, again. The King of Sukhothai, Mahathammaracha II, was present this time.
Realising the hopelessness of further resistance, he surrendered the city and made submission to King Borommaracha I. Mahathammaraja II, was not
deposed, but was left to reign over a portion of his former dominions as a tributary state of Ayutthaya, with his capital at Phitsanulok. The western part
of the Sukhothai dominions, including Chakangrao, was annexed to Ayutthaya. King Borommaracha I combined the two cities of Chakangrao and
Nakhon Chum and called it Khampaeng Phet. The name of Kamphaeng Phet was indicated for the first time in 1397 on a stone inscription.

[Reference: The Royal Chronicles of Ayutthaya - Cushman (2006) - page 12 / A History of Siam - W.A.R. Wood (1924) - page 72]
1387
King Kü Na, the 9th King of Chiang Mai, died around 1387. He was succeeded by his son, Saen Müang Ma. An uncle of the latter, Prince Phrom, made
an attempt to seize the throne but failed and requested the aid of Ayutthaya. King Borommaracha I, seeing an opportunity to extend his power beyond the
Sukhothai dominions dispatched an army to attack Chiang Mai. A fierce battle took place at Saen Sanuk near Chiang Mai, which the Ayutthayan army lost
and they withdrew through Muang li. The Luang Prasoet chronicle of Ayutthaya put this event in 1387. Prince Phrom reconciled with his nephew to
whom he presented the
Phra Singh or Phra Sihing, a sacred Buddha image, obtained by force from Kamphaeng Phet.  

[Reference: A History of Siam - W.A.R. Wood (1924) - page 73]
1388
In 1388 King Borommaracha I went to the North in order to assist the Governor of Kamphaeng Phet against Prince Phrom, ruler of Chiang Saen, who
with his army occupied  the city. Kamphaeng Phet was taken. The king although became ill, returned, but died on the way back to Ayutthaya.

[Reference: The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 12 / Source: Luang Prasoet.]
1388
Prince Thong Lan, 17-year old son of King Borommaracha I ascends the throne - 4th King of Ayutthaya.

[Reference: A History of Siam - W.A.R. Wood (1924) - page 74]
1388
Former King Ramesuan, son of Ramathibodhi I descends to Ayutthaya from Lopburi with an army. He succeed in entering the palace and arrest King
Thong Lan. The latter is executed at the Khok Phraya Monastery. King Thong Lan reigned for seven days. King Ramesuan re-ascends the throne.

[Reference: The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 12 / Source: Phan Canthanumat, British Museum, Reverend
Phonnarat & Phra Cakkraphatdiphong.]
1390
Sukhothai under King Maha Thammaracha II attacks Chiang Mai forces - King Thammaracha of Sukhothai requested the aid of the King of Chiang Mai
to throw off his allegiance with Ayutthaya. The young King of Chiang Mai, Saen Müang Ma (r.1385-1411), came down at the head of an army to assist
the vassal, but this would appear to have been merely a ruse, for the Chiang Mai army was suddenly attacked by night by the Sukhothai forces, and
dispersed with great loss. The young King of Chiang Mai himself only just managed to escape.

[Reference: History of Laos - M.L. Manich Jumsai (2000) - page 54 / A History of Siam - W.A.R. Wood (1924) - page 75]
1393
The King of Cambodia, Kodom Bong, invades Chonburi and Chantabun districts, and removed 7000 of the population back to Cambodia. The Khmer
Pongsa Voda records this invasion in 1373.

[Reference: A History of Siam - W.A.R. Wood (1924) - page 76 / www.geocities.com/khmerchronology - data retrieved on 24 April 2009)]  
1393
King Ramesuan assembled an army and advanced to the Khmer capital, Angkor Thom. The Cambodian forces were routed and the King of Cambodia
escaped by boat; his final fate not recorded. The Crown Prince was captured, and a grandson of King Kodom Bong, named Sri Suriyo Phawong, was set
up as a vassal King, under the tutelage of the Siamese General, Phya Jai Narong, who remained in Cambodia with a garrison of five thousand men. No
less than 90,000 Cambodians were taken away as prisoners to Siam. (According to Cambodian history, this invasion took place in A.D. 1357)  

[Reference: A History of Siam - W.A.R. Wood (1924) - page 76]
1395
Ming envoys, eunuch Zhao Da and Song Fu, lead a maritime voyage to Ayutthaya (with the aim to control trade and execute political and economic
control).

[Reference: The Zheng He Voyages: A Reassessment - Geoff Wade (2004) - Asia Research Institute Working Paper Series No. 31.]
1395
Death of King Ramesuan and throne ascendancy of King Ramaracha, a grandson of King U-Thong - 5th King of Ayutthaya.
1396
A high-ranking envoy [Khun Luang] from the south (likely Sukhothai, possibly Ayutthaya) came to Nan in 1396 to perform the consecration of Chao
Khamtan, the ruler of Nan. The ceremony, consisting in pouring consecrated water over the head of the ruler of Nan, took place at Ta Li. After the
consecration, Chao Khamtan got severe headache and died the same night. The envoy fled, what let us in the supposition that the consecrated water was
poisoned and the ruler of Nan as thus murdered. Chao Si Canta, his son, succeeded him the same year.

[Reference: The Nan Chronicle - Ratchasomphan (Sænluang.) - David K. Wyatt  (1994) - SEAP Publications -page 49 (2.13)]
1397
The rulers of Phrae attacked and captured Nan, after Chao Si Canta was on the throne for one year. The eight king of the Nan dynasty was put to death
in1397. Chao Hung, the younger brother of the King south refuge in the Kingdom of Sukhothai at Chaliang.

[Reference: The Nan Chronicle - Ratchasomphan (Sænluang.) - David K. Wyatt  (1994) - SEAP Publications -page 49 (2.14)]
1398
Throne ascendancy of Maha Thammaracha III of Sukhothai (Sai Luthai).

[Reference: The Rise of Ayudhya - Chranvit Kasetsiri (1976) - App A]
1300 - 1399